The purpose of this proposal is to foster the scientific development and clinical research skills of Kenneth Bilchick, MD, in order that he may become an independent clinical investigator. The University of Virginia (UVA) will provide him with all the resources of this major academic medical center for this proposal, including a dedicated MR research scanner, state-of-the-art echocardiographic imaging equipment, and a fully equipped Stress lab. This proposal will serve as the foundation for the development of an independent academic career under the guidance of mentor Christopher Kramer, M.D., and co-mentor Frederick Epstein, Ph.D. Of note. Dr. Bilchick's career development plan includes completion of a Masters degree in Clinical Investigation. Heart failure (HF) is a major cause of morbidity and mortality affecting nearly 5 million Americans. Dr. Bilchick's long-term research goal is to develop and apply advanced cardiac imaging techniques to patients with heart failure and cardiac arrhythmias. Cardiac resynchronization therapy (CRT) has great potential clinical benefit for patients with HF, but is limited by difficulties identifying appropriate patients and achieving optimal left ventricular (LV) lead placement. This project employs cine DENSE (displacement encoding with stimulated echoes), a novel cardiac magnetic resonance (CMR) imaging protocol that was developed at UVA and yields very high quality strain data even in dilated and thinned left ventricles. The primary hypothesis of the proposal is that CMR with DENSE assessment of circumferential mechanical dyssynchrony and scar imaging is significantly more accurate than echocardiography in predicting CRT response, with nonresponse the likely result when the LV lead is positioned in or near significant scar. Therefore, this prospective study evaluates whether CMR DENSE assessment of the substrate for resynchronization provides more accurate determination of CRT response than echocardiography (specific aim #1) and whether LV lead sites with significant surrounding scar are associated with lack of CRT response (specific aim #2). Study participants will have clinical assessment, cardiac imaging, cardiopulmonary exercise testing, and neurohormonal assessment at baseline and 6 months after the clinical CRT procedure, as well as long-term follow-up for 3 years after CRT. RELEVANCE (See instructions): Heart failure (HF) is a major cause of morbidity and mortality with nearly 5 million Americans affected. CRT has great potential benefit for the most symptomatic HF patients, but its efficacy has been limited by difficulty identifying appropriate candidates. This study of cine DENSE CMR in patients with HF undergoing CRT is of high public health importance as it seeks to improve CRT candidate selection and optimize the procedure. (End of Abstract)